Selective catalytic reduction (SCR) with ammonia is a common means for NOx reduction in gas turbine power plants. It converts nitrogen oxides, also referred to as NOx, with the aid of a catalyst into N2, and water, H2O. The use of three-way catalytic converters has been proposed to avoid the use of ammonia. However they require a fuel to air ratio close to the stoichiometric point. To reduce the oxygen content in the combustion gases a gas turbine plant is proposed in the U.S. 2009/0284013 A1, which comprises a gas turbine, a heat recovery steam generator and a flue gas recirculation. The gas turbine comprises a compressor for air, and a compressor for recirculated flue gas, a burner and a turbine. The input side of heat recovery steam generator is connected to a turbine outlet of the gas turbine. The heat recovery steam generator comprises two boiler outlets. A chimney is connected to the first boiler outlet. The flue gas recirculation connects to the second boiler outlet with a compressor inlet of the compressor for recirculated flue gas. Further, a flue gas treatment device in the form of a three-way catalyst disposed upstream of the waste heat boiler is known from this gas turbine plant.
The proposed plant allows combustion with a fuel to air ratio λ close to one by reducing the oxygen content in the combustor inlet gas. However, the complete stable combustion at close to stoichiometric conditions in the restricted space of a gas turbine combustor is difficult to realize. Additionally, the matching of two compressors (e.g. with respect to mass flows and pressures) on a single shaft is difficult to realize for different operation conditions.